Author: Aaron Beckendorf

69 Articles

A 3D-printed case encloses a number of electronic components. In the top left of the case, a laser diode is mounted. In the top right, the laser beam is shining into a cuvette, which is glowing red from scattered light. In the bottom right, a small breadboard has an integrated circuit and a few parts mounted. In the bottom left is a large red circuit board marked “Rich UNO R3.”

Measuring Nanoparticles By Scattering A Laser

August 30, 2025 by 6 Comments

A fundamental difficulty of working with nanoparticles is that your objects of study are too small for an optical microscope to resolve, and thus measuring their size can be quite a challenge. Of course, if you have a scanning electron microscope, measuring particle size is straightforward. But for less well-equipped labs, a dynamic light scattering system, such as [Etienne]’s OpenDLS, fits the bill.

Dynamic light scattering works by shining a laser beam into a suspension of fine particles, then using a light sensor to measure the intensity of light scattered onto a certain point. As the particles undergo Brownian motion, the intensity of the scattered light changes. Based on the speed with which the scattered light varies, it’s possible to calculate the speed of the moving particles, and thus their size.

The OpenDLS uses a 3D printed and laser-cut frame to hold a small laser diode, which shines into a cuvette, on the side of which is the light sensor. [Etienne] tried a few different options, including a photoresistor and a light sensor designed for Arduino, but eventually chose a photodiode with a two-stage transimpedance amplifier. An Arduino samples the data at 67 kHz, then sends it over serial to a host computer, which uses SciPy and NumPy to analyse the data. Unfortunately, we were about six years late in getting to this story, and the Python program is a bit out of date by now (it was written in Python 2). It shouldn’t, however, be too hard for a motivated hacker to update.

With a standard 188 nm polystyrene dispersion, the OpenDLS calculated a size of 167 nm. Such underestimation seemed to be a persistent issue, probably caused by light being scattered multiple times. More dilution of the suspension would help, but it would also make the signal harder to measure, and the system’s already running near the limits of the hardware.

This isn’t the only creative way to measure the size of small particles, nor even the only way to investigate small particles optically. Of course, if you do have an electron microscope, nanoparticles make a good test target.

A golden robotic hand is shown in the main picture performing the sign for the letter "g": pointing to the left, with all fingers except for the index finger curled. In the top left of the image, a human hand is shown imitating this position.

Ambidextrous Robot Hand Speaks In Signs

August 24, 2025 by 5 Comments

As difficult as it is for a human to learn ambidexterity, it’s quite easy to program into a humanoid robot. After all, a robot doesn’t need to overcome years of muscle memory. Giving a one-handed robot ambidexterity, however, takes some more creativity. [Kelvin Gonzales Amador] managed to do this with his ambidextrous robot hand, capable of signing in either left- or right-handed American Sign Language (ASL).

The essential ingredient is a separate servo motor for each joint in the hand, which allows each joint to bend equally well backward and forward. Nothing physically marks one side as the palm or the back of the hand. To change between left and right-handedness, a servo in the wrist simply turns the hand 180 degrees, the fingers flex in the other direction, and the transformation is complete. [Kelvin] demonstrates this in the video below by having the hand sign out the full ASL alphabet in both the right and left-handed configurations.

The tradeoff of a fully direct drive is that this takes 23 servo motors in the hand itself, plus a much larger servo for the wrist joint. Twenty small servo motors articulate the fingers, and three larger servos control joints within the hand. An Arduino Mega controls the hand with the aid of two PCA9685 PWM drivers. The physical hand itself is made out of 3D-printed PLA and nylon, painted gold for a more striking appearance.

This isn’t the first language-signing robot hand we’ve seen, though it does forgo the second hand. To make this perhaps one of the least efficient machine-to-machine communication protocols, you could also equip it with a sign language translation glove.

A brown plastic circuit board is visible in the middle of the picture, containing an integrated circuit, a resistor, a diode, two capacitors, and some jumper wires going away to the sides.

A Solderless, Soluble Circuit Board

August 19, 2025 by 25 Comments

Anyone who’s spent significant amounts of time salvaging old electronics has probably wished there were a way to take apart a circuit board without desoldering it. [Zeyu Yan] et al seem to have had the same thought, and designed circuit boards that can be dissolved and recycled when they become obsolete. Read the details in the research paper. (PDF)

The researchers printed the circuit boards out of water-soluble PVA, with hollow channels in place of interconnects. After printing the boards, they injected a eutectic gallium-indium liquid metal alloy into these channels, populated the boards with components, making sure that their leads were in contact with the liquid alloy, and finally closed off the channels with PVA glue, which also held the components in place. When the board is ready to recycle, they simply dissolve the board and glue in water. The electric components tend to separate easily from the liquid alloy, and both can be recovered and reused. Even the PVA can be reused: the researchers evaporated the solution left after dissolving a board, broke up the remaining PVA, and extruded it as new filament.
Continue reading “A Solderless, Soluble Circuit Board” →

On the left side of the image, three lit candles are positioned next to each other, so that the flames merge. On the right side, an oscilloscope screen is shown displaying an oscillating waveform.

2025 One Hertz Challenge: A Flaming Oscillator And A New Take On The Candle Clock

August 17, 2025 by 6 Comments

Candle clocks were once an easy way to build a clock without using complex mechanical devices: just observe how quickly a thin candle burns down, mark an identical candle with periodic gradations, and you had a simple timer. These were the first candle-based timekeeping devices, but as [Tim]’s flicker-based oscillator demonstrates, they’re certainly not the only way to keep time with a flame.

Generally speaking, modern candles minimize flickering by using a wick that’s designed to balance the amount of wax and air drawn into the flame. However, when several candles are brought close together, their flames begin to interfere with each other, causing them to flicker in synchrony. The frequency of flickering is a function of gravity and flame diameter alone, so a bundle of three candles will flicker at a fairly constant frequency; in [Tim]’s case, it was about 9.9 Hz.

To sense this oscillation, [Tim] originally used a phototransistor to detect the flame’s light, but he wanted an even simpler solution. He positioned a wire just above the flame, so that as it flickered it would periodically contact the wire. A flame has a different dielectric constant than air does, so the capacitance between this and another wire wrapped around the bundle of candles fluctuates with the flame. To sense this, he used a CH32V003 microcontroller, which reads capacitance, performs some signal processing to get a clean signal, counts oscillations, and uses this time signal to blink an LED once a second. The final result is unusually mesmerizing for a blinking LED.

In something of the reverse of this project, we’ve also seen an oscillator used for an (artificial) candle. There’s also a surprising amount of science that can be learned by studying candles.

Continue reading “2025 One Hertz Challenge: A Flaming Oscillator And A New Take On The Candle Clock” →

A red Sony PSP gaming console is shown, displaying the lines “Audio Mechanica,” “Brek Martin 2006-2025,” and “Waiting for Headphones.”

Running Guitar Effects On A PlayStation Portable

August 13, 2025 by 8 Comments

If your guitar needs more distortion, lower audio fidelity, or another musical effect, you can always shell out some money to get a dedicated piece of hardware. For a less conventional route, though, you could follow [Brek Martin]’s example and reprogram a handheld game console as a digital effects processor.

[Brek] started with a Sony PSP 3000 handheld, with which he had some prior programming experience, having previously written a GPS maps program and an audio recorder for it. The PSP has a microphone input as part of the connector for a headset and remote, though [Brek] found that a Sony remote’s PCB had to be plugged in before the PSP would recognize the microphone. To make things a bit easier to work with, he made a circuit board that connected the remote’s hardware to a microphone jack and an output plug.

[Brek] implemented three effects: a flanger, bitcrusher, and crossover distortion. Crossover distortion distorts the signal as it crosses zero, the bitcrusher reduces sample rate to make the signal choppier, and the flanger mixes the current signal with its variably-delayed copy. [Brek] would have liked to implement more effects, but the program’s lag would have made it impractical. He notes that the program could run more quickly if there were a way to reduce the sample chunk size from 1024 samples, but if there is a way to do so, he has yet to find it.

If you’d like a more dedicated digital audio processor, you can also build one, perhaps using some techniques to reduce lag.

Continue reading “Running Guitar Effects On A PlayStation Portable” →

A pink sine wave is seen against the black background of an oscilloscope display.

Coping With Disappearing Capacitance In A Buck Converter

August 10, 2025 by 25 Comments

Designing a circuit is a lot easier on paper, where components have well-defined values, or lacking that, at least well-defined tolerances. Unfortunately, even keeping percentage tolerances in mind isn’t always enough to make sure that circuits work correctly in the real world, as [Tahmid] demonstrates by diagnosing a buck converter with an oddly strong voltage ripple in the output.

Some voltage ripple is an inherent feature of the buck converter design, but it’s inversely proportional to output capacitance, so most designs include a few smoothing capacitors on the output side. However, at 10 V and a 50% duty cycle, [Tahmit]’s converter had a ripple of 0.75 V, significantly above the predicted variation of 0.45 V. The discrepancy was even greater at 20 V.

The culprit was the effect of higher voltages on the ceramic smoothing capacitors: as the voltage increases, the dielectric barrier in the capacitors becomes less permittive, reducing their capacitance. Fortunately, unlike in the case of electrolytic capacitors, the degradation of ceramic capacitors performance with increasing voltage is usually described in specification sheets, and doesn’t have to be manually measured. After finding the reduced capacitance of his capacitors at 10 V, [Tahmid] calculated a new voltage ripple that was only 14.5% off from the true value.

Anyone who’s had much experience with electronics will have already learned that passive components – particularly capacitors – aren’t as simple as the diagrams make them seem. On the bright side, they are constantly improving.

A filament extruder is shown on a workbench. On the front is a knob and the display of a PID controller. A black geared spool is mounted on the top of the extruder, and on the right, a clear plastic bottle is positioned over a metal rod.

Turning Waste Plastic Into Spools Of Filament

August 1, 2025 by 28 Comments

Despite being a readily-available source of useful plastic, massive numbers of disposable bottles go to waste every day. To remedy this problem (or take advantage of this situation, depending on your perspective) [Igor Tylman] created the PETmachine, an extruder to make 3D printer filament from PET plastic bottles.

The design of the extruder is fairly standard for such machines: a knife mounted to the frame slices the bottle into one long strip, which feeds through a heated extruder onto a spool which pulls the plastic strand through the system. This design stands out, though, in its documentation and ease of assembly. The detailed assembly guides, diagrams, and the lack of crimped or soldered connections all make it evident that this was designed to be built in a classroom. The filament produced is of respectable quality: 1.75 mm diameter, usually within a tolerance of 0.05 mm, as long as the extruder’s temperature and the spool’s speed were properly calibrated. However, printing with the filament does require an all-metal hotend capable of 270 ℃, and a dual-drive extruder is recommended.

One issue with the extruder is that each bottle only produces a short strand of filament, which isn’t sufficient for printing larger objects. Thus, [Igor] also created a filament welder and a spooling machine. The welder uses an induction coil to heat up a steel tube, inside of which the ends of the filament sections are pressed together to create a bond. The filament winder, for its part, can wind with adjustable speed and tension, and uses a moving guide to distribute the filament evenly across the spool, avoiding tangles.

If you’re interested in this kind of extruder, we’ve covered a number of similar designs in the past. The variety of filament welders, however, is a bit more limited.

Thanks to [RomanMal] for the tip!